The present invention relates to information recording apparatus. More particularly, it relates to apparatus for sensing the beginning of the tape or the end of the tape in a magnetic recording apparatus wherein the magnetic record member is contained in a cartridge.
In magnetic recording systems, there has arisen a need for means for determining the approaching end of a tape when the tape is moving in the forward direction or the approaching beginning of the tape when the tape is moving in a reverse direction. In systems provided heretofore, there have been a number of approaches to providing signals representative of those conditions. In one previous approach, a metal foil element is secured to the reverse side of the magnetic record tape a predetermined distance before the end of the tape in either direction, a light source is provided, light from which is reflected by the metalic foil onto a photocell to provide a signal indicative of the presence of the foil element. In a variation of the same approach, a pair of conductive contacts engaged the reverse side of the tape and are shorted by the metalic foil when it engages the contacts. In both of these previous approaches, access must be had to the reverse side of the tape. In other previous approaches to solving the problem, various forms of tachometer devices have been employed to provide count signals representative of the amount of tape remaining on a reel. These have required unduly complex mechanical and electronic structures to provide the required signals. Still others have provided recorded signals on the face of the tape to be detected by a magnetic transducer. These either require a separate playback system and auxiliary data tracks on the tape or they interfere with the intelligence data recorded on the tape itself. In either case the result is undesirable. Further, the recorded signals are subject to being erased inadvertently.
In certain magnetic tape recording systems, the tape is permanently contained within a cartridge such as is shown in the referenced Shroff patents. In such a cartridge, access is not available to the reverse side of the magnetic record member. Further, it is desirable to not apply keying elements to the oxide side of the record member; these would interfere with the normal operation of the recorder system.